Re: Oops in rpc_depopulate with 2.5.62

["Martin J. Bligh" <mbligh@aracnet.com>]

This seems to fix the problem. No idea what it's doing, but it works ;-)

M.

> On Sat, Feb 22, 2003 at 12:49:30AM -0800, Andrew Morton wrote:
>> 
>> Maneesh and Dipankar may be able to plug this one.  I've looked,
>> and apart from a seemingly-unneeded test for !d_unhashed I can't
>> see the problem.
>> 
>> Perhaps the problem lies with a different part of the code.
>> 
>> I cannot reproduce the crash.
> 
> Same with me also. Surprisingly I am getting same oops on 2.5.61.
> Can send .config and ksymoops output if required.
> 
> rpc_rmdir does lookup_hash(), which may return a negative dentry. 
> If a negative dentry is possible at this point then  testing for d_inode 
> in rpc_rmdir() fixes this problem. Like we have in rpc_unlink().
> Probably Trond knows better. 
> 
> Following patch fixes the oops I am seeing in 2.5.61 and should fix
> the oops seen on 2.5.62 also.
> 
> 
> diff -urN linux-2.5.62-bk6/net/sunrpc/rpc_pipe.c
> linux-2.5.62-bk6-rpc_depopulate/net/sunrpc/rpc_pipe.c ---
> linux-2.5.62-bk6/net/sunrpc/rpc_pipe.c	2003-02-24 16:06:46.000000000 +0530
> +++ linux-2.5.62-bk6-rpc_depopulate/net/sunrpc/rpc_pipe.c	2003-02-24
> 16:57:14.000000000 +0530 @@ -665,8 +665,10 @@
>  		error = PTR_ERR(dentry);
>  		goto out_release;
>  	}
> -	rpc_depopulate(dentry);
> -	error = __rpc_rmdir(dir, dentry);
> +	if (dentry->d_inode) {
> +		rpc_depopulate(dentry);
> +		error = __rpc_rmdir(dir, dentry);
> +	}
>  	dput(dentry);
>  out_release:
>  	up(&dir->i_sem);
> 
> 
> 
> Regards
> Maneesh
> 
>> "Martin J. Bligh" <mbligh@aracnet.com> wrote:
>> > 
>> > Getting rpc/nfs bugs on at least two different machines I've seen
>> > and reports of a third from Zwane - all look similar. Anyone got
>> > any bright ideas?
>> > 
>> > M.
>> > 
>> > Unable to handle kernel NULL pointer dereference at virtual address
>> > 0000006c printing eip:
>> > c03415e2
>> > *pde = 358d2001
>> > *pte = 00000000
>> > Oops: 0002
>> > CPU:    1
>> > EIP:    0060:[<c03415e2>]    Not tainted
>> > EFLAGS: 00010206
>> > EIP is at rpc_depopulate+0x22/0xf0
>> > eax: 00000000   ebx: f5133680   ecx: 0000006c   edx: f50afc1c
>> > esi: f50afbf4   edi: f50afbf4   ebp: f50afc08   esp: f50afbec
>> > ds: 007b   es: 007b   ss: 0068
>> > Process mount (pid: 1166, threadinfo=f50ae000 task=f5766d80)
>> > Stack: c01562f0 00000000 f50afbf4 f50afbf4 f5133680 f5133680 f51c1e00
>> > f50afc40  c0341af5 f5133680 f5117880 f7ff9800 f50afcec 00000000
>> >        f50afc34 00000010  00000001 00000000 f5982680 f50afcec 00000000
>> >        f50afc50 c0333066 f5982714  Call Trace:
>> >  [<c01562f0>] lookup_hash+0x70/0xa0
>> >  [<c0341af5>] rpc_rmdir+0x55/0x90
>> >  [<c0333066>] rpc_destroy_client+0x46/0x70
>> >  [<c03330db>] rpc_release_client+0x4b/0x60
>> >  [<c0337bc7>] rpc_release_task+0x1a7/0x1d0
>> >  [<c033754b>] __rpc_execute+0x35b/0x370
>> >  [<c011a980>] default_wake_function+0x0/0x20
>> >  [<c0333274>] rpc_call_sync+0x64/0xa0
>> >  [<c0333287>] rpc_call_sync+0x77/0xa0
>> >  [<c03366b0>] rpc_run_timer+0x0/0xa0
>> >  [<c033e5fb>] rpc_register+0xcb/0x100
>> >  [<c0110000>] mask_and_ack_8259A+0x10/0xf0
>> >  [<c0339d24>] svc_register+0x94/0x100
>> >  [<c0339944>] svc_create+0xd4/0xe0
>> >  [<c01c1fb8>] lockd_up+0x58/0x110
>> >  [<c01a63f4>] nfs_fill_super+0x374/0x3a0
>> >  [<c01a7e90>] nfs_get_sb+0x1f0/0x230
>> >  [<c0150052>] do_kern_mount+0x42/0xa0
>> >  [<c01631e6>] do_add_mount+0x76/0x150
>> >  [<c0133596>] __alloc_pages+0x76/0x2c0
>> >  [<c01634d7>] do_mount+0x147/0x160
>> >  [<c0163908>] sys_mount+0xa8/0x110
>> >  [<c010ae7b>] syscall_call+0x7/0xb
>> > 
>> > Code: f0 ff 48 6c 0f 88 70 09 00 00 f0 fe 0d 00 d2 44 c0 0f 88 6d 
>> > 
>> > Seems to be crashing on the  deference of:
>> > 
>> >         down(&dir->i_sem);
>> > 
>> > in rpc_depopulate. But there's a big comment just above saying:
>> > 
>> > -----------------------
>> > /*
>> >  * FIXME: This probably has races.
>> >  */
>> > static void
>> > rpc_depopulate(struct dentry *parent)
>> > {
>> >         struct inode *dir = parent->d_inode;
>> >         LIST_HEAD(head);
>> >         struct list_head *pos, *next;
>> >         struct dentry *dentry;
>> > 
>> >         down(&dir->i_sem);
>> > 
>> > ------------------
>> > 
>> > Looks like dir is NULL here ... might be dcache_rcu (a recent
>> > dcache_rcu patch fixed the same file) or a race brought out by the
>> > changes.
>> > 
>> > 
>> > -
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> 
> -- 
> Maneesh Soni
> IBM Linux Technology Center, 
> IBM India Software Lab, Bangalore.
> Phone: +91-80-5044999 email: maneesh@in.ibm.com
> http://lse.sourceforge.net/
> 
>